Sync: stop resend if not required

[AlexeyBarabash]

Description

Sync resends bookmarks records even if it is not required.

Steps to Reproduce

1. Establish sync between two browsers
2. Add bookmark A1.com on device A and B1.com on device B
3. Wait > 20 minutes
4. Open inspector and sync extension

Actual result:

5. Possible to see "send-sync-records" category_name="BOOKMARKS" records=... messages even if bookmarks were not changed.

Expected result:

5. No bookmarks records sent if no were changed.

Reproduces how often:

Easily

Brave version (brave://version info)

Brave	0.69.72 Chromium: 76.0.3809.62 (Developer Build) (64-bit)
Revision	7b77856b3aa34d72f246d12340fc1ded8b2c0e83-refs/branch-heads/3809@{#798}
OS	Linux
JavaScript	V8 7.6.303.20

Version/Channel Information:

• Can you reproduce this issue with the current release? yes
• Can you reproduce this issue with the beta channel?
• Can you reproduce this issue with the dev channel?
• Can you reproduce this issue with the nightly channel? yes

Miscellaneous Information:

[LaurenWags]

Verified passed with

Brave	0.66.101 Chromium: 75.0.3770.142 (Official Build) (64-bit)
Revision	8d93477bd18154c67a70a67019cb8032382c55dd-refs/branch-heads/3770@{#1160}
OS	Mac OS X

• Used 0.66.101 for device A and 0.67.112 for device B. (device B is using a version that does not have this fix yet). Added a bookmark to each device, then created sync chain on Device A and joined with device B. Verified device A (with the fix) did not show "send-sync-records" category_name="BOOKMARKS" records=... in the logs multiple times, whereas device B did. Screenshot below - left is device B, right is device A.
  
• Used 0.66.101 for device A and 0.67.112 for device B. Created sync chain on Device A and joined with device B. Then added a bookmark to each device. Verified device A (with the fix) did not show "send-sync-records" category_name="BOOKMARKS" records=... in the logs multiple times. Note - in this second case, Device B did not show "send-sync-records" category_name="BOOKMARKS" records=... in the logs multiple times.

Verification passed on

Brave	0.66.101 Chromium: 75.0.3770.142 (Official Build) (64-bit)
Revision	8d93477bd18154c67a70a67019cb8032382c55dd-refs/branch-heads/3770@{#1160}
OS	Ubuntu 18.04 LTS

For device that created the bookmark, I observed:
"send-sync-records" category_name="BOOKMARKS" records=[{"action":0,
On device that received the bookmark I observed:
"send-sync-records" category_name="BOOKMARKS" records=[{"action":1,
Subsequent "send-sync-records" were not recorded.

Verification PASSED on Win 10 x64 using the following build:

Brave	0.66.101 Chromium: 75.0.3770.142 (Official Build) (64-bit)
Revision	8d93477bd18154c67a70a67019cb8032382c55dd-refs/branch-heads/3770@{#1160}
OS	Windows 10 OS Version 1809 (Build 17763.615)

• ensured that I didn't receive multiple "send-sync-records" category_name="BOOKMARKS" records=[{"... entries within the browser console when there weren't any changes to bookmarks.

[AlexeyBarabash]

Forgot to mention, for more comfortable understanding, it is possible to switch timestamps in Inspector by kebab menu => Settings => Console => Show timestamps.